Processes for producing methionine are well known in the art and are described in, e.g., U.S. Pat. No. 4,069,251, incorporated herein by reference. One of the most prominent side products of such processes is the dipeptide, methionyl-methionine. The hydrolysis of this dipeptide should result in a higher yield of the final product. However, this reaction is subject to various difficulties. One main problem is that by-products of the hydrolysis may interfere with the carbonization reaction taking place during the final step of methionine formation.
According to EP 1 312 611, proteins are degraded to peptides and/or amino acids in supercritical water (that is at a temperature above 355° C. and at a pressure of at least 22 MPa) or high-pressure hot water near the critical point. However, at such high temperatures, highly corrosion resistant and, hence expensive, equipment is necessary and the end product methionine would be subject to thermal degradation (see EP 839 804). These problems can be avoided by carrying out reactions at a lower temperature but the cleavage of methionyl-methionine typically occurs too slowly at temperatures below 200° C. to be desirable for an industrial process.
Thus, there is a need to provide an economically viable process for hydrolyzing methionyl-methionine at reasonable rates while, at the same time, avoiding undesirable side reactions, the degradation of the end product and the need for highly corrosion-resistant materials.